The present invention relates generally to valves for regulating the flow of fluids and, more particularly, to multiport valves for controlling flow of fluids from at least two sources to at least two destinations.
In the manufacture of coated web substrates, for example photographic films and papers, a liquid composition is coated via a specialized coating apparatus, typically a coating die or hopper, onto a moving web substrate. The composition, which may be one of several being coated simultaneously through the same hopper, is delivered to the hopper from a holding vessel via a solution delivery system. Current solution delivery systems in the photographic industry are highly automated and include a number of specialized valves for performing specific functions including, for example, changing flows between vessels, changing inline filters, purging of entrained air from the components of the system, and delivering coating compositions and flush water to the coating hopper.
Bubbles in solution (in the form of entrained air) are a reality of the modem high speed methods to coat complex photographic films in papers. If not removed prior to coating, bubbles are a major source of machine down time and coated waste. A single bubble, 30 microns or larger can cause a coating defect and must be avoided. Bubbles may be introduced into coating solutions in many ways. Bubbles may be directly introduced as a result of voids or air pockets created in various system components. Bubbles may be the result of entrained gases present in the liquids flowing through the system. Bubbles may further be the result of dissolved gases released as components of the coating solutions are xe2x80x9cmeltedxe2x80x9d from the solid to the liquid state. As a result, bubbles must be effectively removed from the coating system to reduce coating waste.
Bubbles are initially removed and minimized by known deaeration processes. Once the bubbles are removed from the coating solution, the coating solution delivery system is prepared. The solution delivery system (SDS) (lines and components) are prepared by first filling the system with deaerated high purity water at 40xc2x0 C. This water fill step is designed to eliminate all air and bubbles from the SDS. In the next step, the water is displaced (purged) by bubble free coating solution. However, SDS components, particularly the valves, can be difficult to purge. Dead legs, threads, cracks, and valve cavities can all produce bubble traps that eventually release bubbles during the coating operation (as a result of a flow rate change, some other upset, or just by chance).
Commercially available valves (ball valves, etc.) typically have many internal areas such as crevices, pipe threads, passageways, and valve chambers wherein air can be trapped and fail to be purged during a purge cycle with flush water. In addition, commercially available valves do not have all of the routing features needed for delivering both coating compositions and flush water to a coating apparatus. In particular, commercially available valves do not allow for purging of coating solution from the SDS to drain, while the coating hopper is draining or flushing independently of the SDS.
It is therefore an object of the invention to provide an improved multiport valve wherein the potential for the trapping of air leading to the formation of bubbles is reduced.
It is a further object of the invention to provide an improved multiport valve wherein residual coating composition may be readily removed by flush water.
It is still a further object of the invention to provide an improved multiport coat select valve wherein the solution delivery system may be purged to drain while a connected hopper is draining or being flushed independent of the solution delivery system.
Briefly stated, these and numerous other features, objects, and advantages of the present invention will become readily apparent upon a reading of the detailed description, claims and drawings set forth herein. These features, objects, and advantages are accomplished by a multiport valve for regulating flow of liquid therethrough originating from at least two sources comprising:
a first cylindrical valve chamber having a first inlet port and a first outlet port, the first inlet port tangentially intercepting the first cylindrical valve chamber;
a first piston residing in the first cylindrical valve chamber, the first piston being movable to engage and disengage with a first valve seat located at the first outlet port;
a second cylindrical valve chamber having a second inlet port and a second outlet port;
a second piston residing in the second cylindrical valve chamber, the second piston being movable to engage and disengage with a second valve seat located at the second inlet port;
a primary liquid inlet port for delivering liquid to an internal conduit, the internal conduit connecting with and being coaxial with the second inlet port, the internal conduit also connecting with and being coaxial with a alternative inlet port in an intermediate cylindrical valve chamber, the intermediate cylindrical valve chamber having a third inlet port and a third outlet port, the third inlet port being connected to and coaxial with the first outlet port, the third outlet port tangentially intercepting the intermediate cylindrical valve chamber; and
a third piston residing in the intermediate cylindrical valve chamber, the third piston being movable to engage and disengage with a third valve seat located at the alternative inlet port.
The multiport valve of the present invention is preferably oriented such that the third outlet port is substantially horizontal and tangentially intercepts the intermediate cylindrical valve chamber at a top surface thereof. Each of the valve seats are positioned in a respective end wall of the cylindrical valve chambers. The transition from cylindrical wall to end wall should be radiused.
The first inlet port, tangentially intercepting the first cylindrical valve chamber, creates a swirling or sweeping flow path through the first cylindrical valve chamber allowing bubbles to be swept therefrom. Similarly, the third outlet port, tangentially intercepting the intermediate cylindrical valve chamber, creates a swirling or sweeping flow path through the intermediate cylindrical valve chamber allowing bubbles to be swept therefrom. In addition, the tangential connections aid in avoiding bubble traps in the valve chambers.
It is preferred that each of the pistons is independently controlled and actuated. This allows for selection of flow path therethrough originating from one of two sources and transmitted to one of two destinations.